The research objectives are concerned with a continuing search for principles operating in the nervous system that organize the non-reflexive behaviors, particularly those that are periodic. All of the research will be performed on the sea hare, Aplysia californica (Mollusca: Opisthobranchia) and other related mollusks. The methods of research will be very broadly based. They will include quantitative behavioral measurements, multi-unit and single neuron recordings in intact subjects and dissected (in vitro) preparations, electron microscopy of nervous tissue, the use of organ-cultured ganglia and biochemical measurements on whole ganglia and on single neurons. The titles of the six major projects are as follows: I. The nature and mechanism of action of the egg-laying hormone on behavior. II. Morphological, electrophysiological and biochemical studies of the circadian rhythm in the eye. III. CNS organization leading to the circadian locomotor rhythm. IV. Synaptic organization of a neuron with a circadian rhythm and its relevance for entrainment by photoperiod. V. The synthesis and turnover of proteins in single neurons in relationship to their activity and circadian rhythm. VI. Dynamic aspects of long-term neuronal interactions studied under organ-culture conditions.